[quote author="TomWaterman"]Yeah you're right I suppose. I was specifically thinking of a few people/companies I know working on similar ideas/solutions, one of which involved elaborate daughter/adapter cards and local regulators to enable 500 series operation and the other required large multi-pin backplane connectors to hugely update the feature set with things such as 8 aux/busses for mixing, digital I/O etc.
All of which require upto 4 layer backplanes with 40+ pins.[/quote]
I can imagine. My own plans are much more pedestrian: power, XLR in, XLR out. While I am planning to build stereo compressors in this format, I intend to make those doublewide modules with no over-the-backplane link signals or the like. The only feature I would consider adding (to the expanded 41612-connector) would be a simple unbalanced send/return-insert for sidechains.
[quote author="TomWaterman"]Your plan sounds good indeed, with an extra connector on the board. Have you got rear mounted XLRs and the two connectors on a 2-layer backplane?[/quote]
Yes, after a fashion. The EDACs are PCB-mounted. Originally I wanted to use Neutrik PCB-mount XLRs, but a few prelim tests showed quite a bit of flex stress on their solder connections. The new plan is to have regular B-series panel mount XLRs with very short (~5mm) wires running through oversized PCB holes to solder tabs. The idea is that you mount the backplane to the rear panel with standoffs connected inline with the EDAC's mounting holes. I do have to work a bit more on the mechanical side, but those Neutrik B-series XLRs mount from the inside of the panel, so you can remove a (sub)backplane PCB without desoldering anything.
[quote author="TomWaterman"]If I understand you correctly, the only wiring needed would be linking power between mini-backplanes across the rear of the rack?[/quote]
Indeed. Another thing I'm looking into is giving each PCB its own local 317/337 regulator, which would be mounted to the inside of the rear panel right above the XLRs. The idea is that it's much easier from a heat management perspective to have five regulator pairs spread across the case each supplying 260mA max than one big reg pair delivering up to 1.3A in a fully loaded rack. 317s cost nothing anyway, and this scheme won't hurt inter-module supply immunity either.
JDB.
[What you mentioned about adapters did get me thinking, though. For my own personal use I expect maybe 20% true-500 EDAC vs 80% 41612, so it may make sense to just do the backplane boards in 41612 and have small adapters to translate between the two. This would give the 'native' 41612-designs some 10mm extra space, which wouldn't hurt, at a negligible increase in main case depth. Must ponder this some more.]